1. Field of the Invention
This invention relates to slide fasteners and more particularly to a slide fastener assembly to the type in which top end stops are allowed to enter the interior of a slider.
2. Prior Art
Numerous slide fasteners of the type described are known in the art. A typical example of such slide fasteners is illustrated in FIG. 8, wherein the slider fastener is shown in fully closed disposition with both stringer tapes 10,11 brought together at an end of the fastener and attached by a sewn seam M to a garment, not shown. In this disposition, the top end stops 12,13 are trapped and locked between a diamond 14 and respective side flanges of a slider 15. The beaded edges 16,17 of the tapes 10,11 are devoid of fastener elements 18 and extend from the respective end stops 12,13 to the seam M near the upper ends of the tapes 10,11. The edges 16,17 are spread apart to assume an inverted Y-shape. The angle at which the Y-shaped region of the beaded edges 16,17 spreads or flares is determined by and dependent upon an angle .theta. of the diamond 14. The diamond angle .theta. is also an important factor bearing upon the resistance which is encountered during starting movement of the slider 15 in a direction to open or separate the fastener. The starting resistance is also variable with the coefficient of friction between the diamond 14 and the end stops 12,13, such coefficient of friction being dependent upon the material used for these parts. The starting resistance may further be variable due to the angles .alpha. and .beta. at which the beaded edges 16 and 17 respectively flex with respect to the longitudinal axis of the end stops 12,13. The slider starting resistance decreases as the the angles .alpha. and .beta. decrease. However, if these angles were to be reduced without changing the diamond angle .theta., this reduction could be done by locating the sewn seam M of the beaded edges 16,17 more remotely from the end stops 12,13. Such a change would however result in fastener stringers being left unclosed at the top end of the fastener.
On the other hand, the diamond angle .theta. is required to be about 50 degrees in order to maintain the normal satisfactory operation of opening and closing the fastener (i.e. to disengage and engage the rows of fastener elements 18), and hence cannot be reduced too greatly.